In outer space, you might not recognize the Big Dipper. The stars that form this constellation exist in 3-D not 2-D—so the star pattern changes with your viewpoint. Take another look at the Big Dipper.

In the late 1970s a group of researchers led by physicist Luis Alvarez and geologist Walter Alvarez made an important discovery. While analyzing rock samples from 65 million years ago, the father-son team measured exceptionally high concentrations of a rare element, iridium.